(a) Field of the Invention
The present invention relates to a microlens manufacturing method and a microlens injection mold manufacturing method. More specifically, the present invention relates to a method for precisely and easily manufacturing various microlenses by using an X-ray lithography technology which utilizes synchrotron radiation of a radiation accelerator.
(b) Description of the Related Art
Conventional microlens manufacturing methods are: injection molding microlens arrays by using precisely and mechanically cut dies; a planar array method that varies the refractive index through an ion exchange technique; and a method of photoresist patterning and melting using an ultraviolet lithography process.
A method for manufacturing a spherical microlens arrays by a PolyMethylMethAcrylate(PMAA) patterning and melting process which uses an IMM (Institute of Microtechnology Mainzxe2x80x94a German Lab.) process and a conventional X-ray lithography process is shown in FIG. 1.
FIG. 1 shows a spherical lens manufacturing process by using the conventional X-ray lithography process.
As shown in FIG. 1, the PMMA or sensitive film 2 is coated on a substrate 1, and a cylindrical pattern 2a is generated via an exposure and development process using an X-ray mask 3. The X-rays are exposed on the substrate 1 through a filter membrane 4. A heating process is performed on the coated and exposed substrate at a predetermined temperature so that the cylindrical PMMA is melted. When the cylindrical PMMA is cooled, a spherical lens 2b as shown in the drawing is finally manufactured. The diameter of the lens is determined by the diameter of the cylinder, and the diameter is determined before a heating process is performed on the cylinder. The height of the lens is determined by the diameter and height of the cylinder, as well as the temperature of the heating process, before the heating process is performed on the cylinder.
However, the conventional microlens manufacturing method has the following problems.
First, the techniques which use precision machine work and melting methods have difficulty in handling the machines and in implementing the lens types as only semi-cylindrical or semi-spherical lens types can be produced. That is, ball type or aspherical lenses cannot be manufactured, it is difficult to manufacture microlenses, and a precise controller for controlling working blades is required.
Second, to obtain desired microlens shapes and optical characteristics in the conventional melting techniques, temperature adjustments, and flow controls of the photoresist at the time of the melting process must be precisely performed, but, adjustments of a reproducible heating process is difficult, and it is difficult to fabricate thick photoresist so that it is difficult to manufacture lenses of a large size.
It is an object of the present invention to provide a method for precisely and easily manufacturing microlenses.
In one aspect of the present invention, a microlens manufacturing method using X-ray lithography comprises the steps of: (a) positioning an X-ray mask for manufacturing the microlens on a substrate on which a sensitive film is formed, and arranging a rotation axis of the substrate and a central axis of the X-ray mask; (b) exposing X-rays to the X-ray mask to expose the sensitive film while fixing the X-ray mask and rotating the substrate; and (c) developing the sensitive film to form the microlens.
In the step (b), the substrate is moved back and forth in an X-axis direction to make the rotation axis of the substrate identical with the central axis of the X-ray mask, and the substrate is moved back and forth in the Y-axis direction to adjust a thickness of the sensitive film exposed by the X-ray mask.
The X-ray mask comprises: a mask substrate permeable to X-rays; a holder fixedly installed on the mask substrate and having a hole; and an absorbing member for absorbing X-rays, including an inserter removably formed in the hole, and having a microlens form.
In the step (b), the substrate is positioned in a direction vertical to the absorbing member of the X-ray mask, and the substrate is rotated on the rotation axis 360xc2x0 to be exposed.
Protrusions are formed on the inserter of the absorbing member of the X-ray mask, and installing holes corresponding to the protrusions are formed on the hole of the holder of the X-ray mask.
First protrusions are formed at an end of the inserter of the absorbing member, and first installing holes are formed at positions corresponding to the first protrusions, and second installing holes are formed at a side of the inserter of the absorbing member, and second protrusions are formed on the positions corresponding to the second installing holes of the hole of the holder.